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•IFN-I alters B-1 cell subsets in SCD.•IFN-I enhances TI immune responses and the production of RBC autoantibodies in SCD.

•COVID-19 mRNA vaccination has a good risk-benefit profile in individuals with sickle cell disease.•This study offers some assurances to the sickle cell disease community and their providers about the safety and efficacy of mRNA vaccines.

Pain is the primary symptomatic manifestation of sickle cell disease (SCD), an inherited hemoglobinopathy. The characteristics that influence pain experiences and outcomes in SCD are not fully understood. The primary objective of this study was to use multivariable modeling to examine associations of biopsychosocial variables with a disease-specific measure of pain interference known as pain impact. We conducted a secondary analysis of data from the Global Research Network for Data and Discovery national SCD registry. A total of 657 children and adults with SCD were included in the analysis. This sample was 60% female with a median age of 34 (interquartile range 26–42 years) and a chronic pain prevalence of 64%. The model accounted for 58% of the variance in pain impact. Low social (P < .001) and emotional (P < .001) functioning, increasing age (P = .004), low income (P < .001), and high acute painful episodes (P = .007) were most strongly associated with high pain impact in our multivariable model. Additionally, multivariable modeling of pain severity and physical function in 2 comparable samples of registry participants revealed that increasing age and low social functioning were also strongly associated with higher pain severity and low physical functioning. Overall, the results suggest that social and emotional functioning are more strongly associated with pain impact in individuals with SCD than previously studied biological modifiers such as SCD genotype, hemoglobin, and percentage fetal hemoglobin. Future research using longitudinally collected data is needed to confirm these findings.

•Heme drives a coordinated functional and metabolic reprogramming of macrophages via suppression of efferocytosis and mitochondrial remodeling.•Macrophage metabolic rewiring by heme scavenging or PGC1α/PPARγ modulation promotes tissue damage and inflammation resolution in SCD.

Crizanlizumab is an anti–P-selectin monoclonal antibody indicated to reduce the frequency/prevent recurrence of vaso-occlusive crises (VOCs) in patients with sickle cell disease (SCD) aged ≥16 years. This analysis of an ongoing phase 2, nonrandomized, open-label study reports the pharmacokinetics (PK), pharmacodynamics (PD), safety, and efficacy of crizanlizumab 5.0 mg/kg (N = 45) and 7.5 mg/kg (N = 12) in patients with SCD with a history of VOCs. The median treatment duration was 104.7 and 85.7 weeks in the 5.0 and 7.5 mg/kg groups, respectively. For both doses, serum crizanlizumab concentrations rose to near maximum levels shortly after infusion, and near complete and sustained ex vivo P-selectin inhibition was observed. Grade ≥3 adverse events (AEs) occurred in 48.9% and 33.3% of patients in the 5.0 and 7.5 mg/kg groups, respectively; only 1 event was deemed treatment-related (7.5 mg/kg group). No treatment-related serious AEs occurred. One infusion-related reaction was recorded (5.0 mg/kg, grade 2 “pain during infusion”), which resolved without treatment withdrawal. Infections occurred in 57.8% and 41.7% of patients in the 5.0 and 7.5 mg/kg groups, respectively; none were drug-related. No treatment-related bleeding events were reported. No patients developed immunogenicity. The median (range) absolute reduction from baseline in the annualized rate of VOCs leading to a health care visit was −0.88 (−14.7 to 13.3) and −0.93 (−2.0 to 0.4) in the 5.0 and 7.5 mg/kg groups, respectively. Results here demonstrate the PK/PD properties of crizanlizumab in patients with SCD and the potential sustained efficacy and long-term safety of the drug after >12 months’ treatment. This trial was registered at www.clinicaltrials.gov as #NCT03264989.

•Results from SOLACE-adults demonstrate the PK and PD properties of crizanlizumab in patients with SCD during long-term treatment.•Results also show that no new safety signals were identified and the efficacy of crizanlizumab was consistent with that seen in SUSTAIN.

•A novel image flow cytometric machine learning tool was developed that robustly identified sickled cells and their constituent hemoglobin.•Multiple mechanisms of resistance are offered by sickle/sickle trait red blood cells against Babesia, especially in low-oxygen environments.

Sickle red blood cells (RBCs) represent a naturally existing host-cell resistance mechanism to hemoparasite infections. We investigate the basis of this resistance using Babesia divergens grown in sickle (SS) and sickle trait (AS) cells. We found that oxygenation and its corresponding effect on RBC sickling, frequency of fetal hemoglobin positive (HbF+) cells, cellular redox environment, and parasite proliferation dynamics, all played a role in supporting or inhibiting Babesia proliferation. To identify cellular determinants that supported infection, an image flow cytometric tool was developed that could identify sickled cells and constituent Hb. We showed that hypoxic conditions impaired parasite growth in both SS and AS cells. Furthermore, cell sickling was alleviated by oxygenation (hyperoxic conditions), which decreased inhibition of parasite proliferation in SS cells. Interestingly, our tool identified HbF+-SS as host-cells of choice under both hypoxic and hyperoxic conditions, which was confirmed using cord RBCs containing high amounts of HbF+ cells. Uninfected SS cells showed a higher reactive oxygen species–containing environment, than AA or AS cells, which was further perturbed on infection. In hostile SS cells we found that Babesia alters its subpopulation structure, with 1N dominance under hypoxic conditions yielding to equivalent ratios of all parasite forms at hyperoxic conditions, favorable for growth. Multiple factors, including oxygenation and its impact on cell shape, HbF positivity, redox status, and parasite pleiotropy allow Babesia propagation in sickle RBCs. Our studies provide a cellular and molecular basis of natural resistance to Babesia, which will aid in defining novel therapies against human babesiosis.

•Dietary iron restriction protects against both SCD vaso-occlusion and organ damage.•The benefits of dietary iron restriction in SCD are potentially mediated by regulation of gut microbiota-host crosstalk.

Sickle cell disease (SCD) is an inherited disorder resulting from a β-globin gene mutation, and SCD patients experience erythrocyte sickling, vaso-occlusive episodes (VOE), and progressive organ damage. Chronic hemolysis, inflammation, and repeated red blood cell transfusions in SCD can disrupt iron homeostasis. Patients who receive multiple blood transfusions develop iron overload, and another subpopulation of SCD patients manifest iron deficiency. To elucidate connections between dietary iron, the microbiome, and SCD pathogenesis, we treated SCD mice with an iron-restricted diet (IRD). IRD treatment reduced iron availability and hemolysis, decreased acute VOE, and ameliorated chronic organ damage in SCD mice. Our results extend previous studies indicating that the gut microbiota regulate disease in SCD mice. IRD alters microbiota load and improves gut integrity, together preventing crosstalk between the gut microbiome and inflammatory factors such as aged neutrophils, dampening VOE, and organ damage. These findings provide strong evidence for the therapeutic potential of manipulating iron homeostasis and the gut microbiome to ameliorate SCD pathophysiology. Many treatments, which are under development, focus on lowering the systemic iron concentration to relieve disease complications, and our data suggest that iron-induced changes in microbiota load and gut integrity are related- and novel-therapeutic targets.

Background: Crizanlizumab is a novel inhibitor of P-selectin, a key player in multicellular adhesion and inflammatory signaling, that leads to vaso-occlusion in sickle cell disease (SCD).Objectives: The SOLACE-adults study evaluated the pharmacokinetics, pharmacodynamics (P-selectin inhibition), safety, and efficacy of crizanlizumab, with or without hydroxyurea/hydroxycarbamide, in patients with SCD.Design: Phase II, single-arm, multicenter study.Methods: Patients with SCD aged 16–70 years, with ⩾1 vaso-occlusive crisis (VOC) within 12 months before screening, received crizanlizumab 5.0 or 7.5 mg/kg intravenous infusion every 4 weeks; dose groups were enrolled sequentially.Results: Of 57 patients enrolled, 45 received crizanlizumab 5.0 mg/kg and 12 received 7.5 mg/kg for a median duration of 206 and 170 weeks, respectively. Crizanlizumab concentrations reached maximum levels after a 30-min infusion and remained steady for 6 h, without significant accumulation. P-selectin inhibition was nearly complete for both doses. The median (interquartile range) absolute change in the annualized rate of VOCs leading to healthcare visit from baseline was −0.79 (−3.04, 2.01) in the 5.0 mg/kg group and −0.98 (−1.11, −0.41) in the 7.5 mg/kg group. All patients experienced at least one adverse event (AE), with no apparent differences between the two doses in the frequency and severity of AEs. Grade ⩾3 AEs occurred in 60% of the 5.0 mg/kg group and 58% of the 7.5 mg/kg group. Two patients in the 5.0 mg/kg group and one in the 7.5 mg/kg group had severe crizanlizumab-related infusion-related reactions, which resolved with treatment. No patients developed antibodies against crizanlizumab.Conclusion: Crizanlizumab 5.0 and 7.5 mg/kg demonstrated a dose-proportional increase in exposure, sustained P-selectin inhibition, a tolerable safety profile, and a sustained reduction in VOCs leading to healthcare visit. This suggests that crizanlizumab is a useful treatment option for patients with SCD who have experienced VOCs.Trial Registration: NCT03264989

Sickle cell disease (SCD) is characterized by hemolytic anemia, which can trigger oxidative stress, inflammation, and tissue injury that contribute to disease complications. Bone marrow mesenchymal stromal cells (MSCs) tightly regulate hematopoietic stem cell (HSC) homeostasis in health and disease, but their functionality in SCD remains unclear. We identified for the first time that murine SCD MSCs have altered gene signatures, reduced stem cell properties, and increased oxidative stress, due in part to hemolysis. Murine SCD MSCs had lower HSC maintenance ability in vitro and in vivo, as manifested by increased HSC mobilization and decreased HSC engraftment after transplant. Activation of Toll-like receptor-4 through p65 in MSCs further contributed to MSC dysfunction. Transfusions led to an improved MSC and HSC oxidative state in SCD mice. Improving the regulation between MSCs and HSCs has vital implications for enhancing clinical HSC transplantation and gene therapy outcomes and for identification of new molecular targets for alleviating SCD complications.

Patients with sickle cell disease (SCD) suffer from intravascular hemolysis-associated vascular injury and tissue damage. Classical monocytes (CMo), which are the most abundant of circulating monocytes, are activated in SCD, but the cause and consequences of activation remain incompletely understood. We found a positive correlation between total plasma heme levels and circulating interferon-α (IFN-α) in patients with SCD along with upregulation of the type I IFN (IFN-I) inducible genes in sort-purified SCD patients’ CMo by transcriptome analysis. We demonstrated that hemolysis led to IFN-I expression, predominantly by mouse liver monocyte and macrophages (Mⲫ), primarily through Tank kinase binding 1 (TBK1)/IκB kinase-ε (IKKε) but not TLR4. In response to hemolysis-induced IFN-I, mouse CMo migrated to the liver and differentiated into monocyte-derived Mⲫ, increasing their numbers by sixfold with acute hemin treatment. Hemolysis-driven IFN-I activity also led to the induction of Fc receptor CD64 expression on monocyte and Mⲫ populations, enhancing alloantibody-mediated erythrophagocytosis in SCD both in vivo in mice and in in vitro human cultures. Altogether, these data demonstrate IFN-I response to hemolysis as a novel activation pathway in monocytes and Mⲫ in SCD, opening the possibility for development of IFN-I-based diagnostics and therapeutics against alloantibody-mediated erythrophagocytosis.

Patients with sickle cell disease (SCD) suffer from intravascular hemolysis-associated vascular injury and tissue damage. Classical monocytes (CMo), which are the most abundant of circulating monocytes, are activated in SCD, but the cause and consequences of activation remain incompletely understood. We found a positive correlation between total plasma heme levels and circulating interferon-α (IFN-α) in patients with SCD along with upregulation of the type I IFN (IFN-I) inducible genes in sort-purified SCD patients' CMo by transcriptome analysis. We demonstrated that hemolysis led to IFN-I expression, predominantly by mouse liver monocyte and macrophages (Mⲫ), primarily through Tank kinase binding 1 (TBK1)/IκB kinase-ε (IKKε) but not TLR4. In response to hemolysis-induced IFN-I, mouse CMo migrated to the liver and differentiated into monocyte-derived Mⲫ, increasing their numbers by sixfold with acute hemin treatment. Hemolysis-driven IFN-I activity also led to the induction of Fc receptor CD64 expression on monocyte and Mⲫ populations, enhancing alloantibody-mediated erythrophagocytosis in SCD both in vivo in mice and in in vitro human cultures. Altogether, these data demonstrate IFN-I response to hemolysis as a novel activation pathway in monocytes and Mⲫ in SCD, opening the possibility for development of IFN-I-based diagnostics and therapeutics against alloantibody-mediated erythrophagocytosis.

Red blood cell alloimmunization remains a barrier for safe and effective transfusions in sickle cell disease (SCD), but the associated risk factors remain largely unknown. Intravascular hemolysis, a hallmark of SCD, results in the release of heme with potent immunomodulatory activity, although its effect on SCD humoral response, specifically alloimmunization, remains unclear. Here, we found that cell-free heme suppresses human B-cell plasmablast and plasma cell differentiation by inhibiting the DOCK8/STAT3 signaling pathway, which is critical for B-cell activation, as well as by upregulating heme oxygenase 1 (HO-1) through its enzymatic byproducts, carbon monoxide and biliverdin. Whereas nonalloimmunized SCD B cells were inhibited by exogenous heme, B cells from the alloimmunized group were nonresponsive to heme inhibition and readily differentiated into plasma cells. Consistent with a differential B-cell response to hemolysis, we found elevated B-cell basal levels of DOCK8 and higher HO-1–mediated inhibition of activated B cells in nonalloimmunized compared with alloimmunized SCD patients. To overcome the alloimmunized B-cell heme insensitivity, we screened several heme-binding molecules and identified quinine as a potent inhibitor of B-cell activity, reversing the resistance to heme suppression in alloimmunized patients. B-cell inhibition by quinine occurred only in the presence of heme and through HO-1 induction. Altogether, these data suggest that hemolysis can dampen the humoral B-cell response and that B-cell heme responsiveness maybe a determinant of alloimmunization risk in SCD. By restoring B-cell heme sensitivity, quinine may have therapeutic potential to prevent and inhibit alloimmunization in SCD patients.

Red blood cell alloimmunization remains a barrier for safe and effective transfusions in sickle cell disease (SCD), but the associated risk factors remain largely unknown. Intravascular hemolysis, a hallmark of SCD, results in the release of heme with potent immunomodulatory activity, although its effect on SCD humoral response, specifically alloimmunization, remains unclear. Here, we found that cell-free heme suppresses human B-cell plasmablast and plasma cell differentiation by inhibiting the DOCK8/STAT3 signaling pathway, which is critical for B-cell activation, as well as by upregulating heme oxygenase 1 (HO-1) through its enzymatic byproducts, carbon monoxide and biliverdin. Whereas nonalloimmunized SCD B cells were inhibited by exogenous heme, B cells from the alloimmunized group were nonresponsive to heme inhibition and readily differentiated into plasma cells. Consistent with a differential B-cell response to hemolysis, we found elevated B-cell basal levels of DOCK8 and higher HO-1–mediated inhibition of activated B cells in nonalloimmunized compared with alloimmunized SCD patients. To overcome the alloimmunized B-cell heme insensitivity, we screened several heme-binding molecules and identified quinine as a potent inhibitor of B-cell activity, reversing the resistance to heme suppression in alloimmunized patients. B-cell inhibition by quinine occurred only in the presence of heme and through HO-1 induction. Altogether, these data suggest that hemolysis can dampen the humoral B-cell response and that B-cell heme responsiveness maybe a determinant of alloimmunization risk in SCD. By restoring B-cell heme sensitivity, quinine may have therapeutic potential to prevent and inhibit alloimmunization in SCD patients.

We aimed to identify predictors of outcomes and survival in patients living in 4 major metropolitan areas who had sickle cell disease (SCD) and COVID-19 to inform best approaches to prevention and care. Data were collected at baseline and during the clinical course in SCD patients diagnosed with COVID-19 in four COVID-19 epicenters. Patients were followed up posthospital discharge for up to 3 months. Of sixty-six SCD patients with COVID-19, fifty patients (75%) required hospitalization, and seven died (10.6%). Patients with preexisting kidney disease (chronic kidney disease) were more likely to be hospitalized. The most common presenting symptom was vaso-occlusive pain. Acute chest syndrome occurred in 30 (60%) of the 50 hospitalized patients and in all who died. Older age and histories of pulmonary hypertension, congestive heart failure, chronic kidney disease, and stroke were more prevalent in patients who died, as were higher creatinine, lactate dehydrogenase, and D-dimer levels. Anticoagulation use while inpatient was twice less common in patients who died. All deaths occurred in individuals not taking hydroxyurea or any other SCD-modifying therapy. Patients with SCD and COVID-19 exhibited a broad range of disease severity. We cannot definitively state that the overall mortality is higher in patients with SCD, although our case fatality rate was ∼10% compared with ∼3% in the general population, despite a median age of 34 years. Individuals with SCD aged >50 years, with preexisting cardiopulmonary, renal disease, and/or stroke not receiving hydroxyurea, who present with high serum creatinine, lactate dehydrogenase, and D-dimer levels, are at higher risk of death, irrespective of genotype or sex.

We aimed to identify predictors of outcomes and survival in patients living in 4 major metropolitan areas who had sickle cell disease (SCD) and COVID-19 to inform best approaches to prevention and care. Data were collected at baseline and during the clinical course in SCD patients diagnosed with COVID-19 in four COVID-19 epicenters. Patients were followed up posthospital discharge for up to 3 months. Of sixty-six SCD patients with COVID-19, fifty patients (75%) required hospitalization, and seven died (10.6%). Patients with preexisting kidney disease (chronic kidney disease) were more likely to be hospitalized. The most common presenting symptom was vaso-occlusive pain. Acute chest syndrome occurred in 30 (60%) of the 50 hospitalized patients and in all who died. Older age and histories of pulmonary hypertension, congestive heart failure, chronic kidney disease, and stroke were more prevalent in patients who died, as were higher creatinine, lactate dehydrogenase, and D-dimer levels. Anticoagulation use while inpatient was twice less common in patients who died. All deaths occurred in individuals not taking hydroxyurea or any other SCD-modifying therapy. Patients with SCD and COVID-19 exhibited a broad range of disease severity. We cannot definitively state that the overall mortality is higher in patients with SCD, although our case fatality rate was ∼10% compared with ∼3% in the general population, despite a median age of 34 years. Individuals with SCD aged >50 years, with preexisting cardiopulmonary, renal disease, and/or stroke not receiving hydroxyurea, who present with high serum creatinine, lactate dehydrogenase, and D-dimer levels, are at higher risk of death, irrespective of genotype or sex.

Sickle cell disease (SCD) is the most common inherited blood disorder in the United States. It is a medically and socially complex, multisystem illness that affects individuals throughout the lifespan. Given improvements in care, most children with SCD survive into adulthood. However, access to adult sickle cell care is poor in many parts of the United States, resulting in increased acute care utilization, disjointed care delivery, and early mortality for patients. A dearth of nonmalignant hematology providers, the lack of a national SCD registry, and the absence of a centralized infrastructure to facilitate comparative quality assessment compounds these issues. As part of a workshop designed to train health care professionals in the skills necessary to establish clinical centers focused on the management of adults living with SCD, we defined an SCD center, elucidated required elements of a comprehensive adult SCD center, and discussed different models of care. There are also important economic impacts of these centers at an institutional and health system level. As more clinicians are trained in providing adult-focused SCD care, center designation will enhance the ability to undertake quality improvement and compare outcomes between SCD centers. Activities will include an assessment of the clinical effectiveness of expanded access to care, the implementation of SCD guidelines, and the efficacy of newly approved targeted medications. Details of this effort are provided.

Sickle cell disease (SCD) is the most common inherited blood disorder in the United States. It is a medically and socially complex, multisystem illness that affects individuals throughout the lifespan. Given improvements in care, most children with SCD survive into adulthood. However, access to adult sickle cell care is poor in many parts of the United States, resulting in increased acute care utilization, disjointed care delivery, and early mortality for patients. A dearth of nonmalignant hematology providers, the lack of a national SCD registry, and the absence of a centralized infrastructure to facilitate comparative quality assessment compounds these issues. As part of a workshop designed to train health care professionals in the skills necessary to establish clinical centers focused on the management of adults living with SCD, we defined an SCD center, elucidated required elements of a comprehensive adult SCD center, and discussed different models of care. There are also important economic impacts of these centers at an institutional and health system level. As more clinicians are trained in providing adult-focused SCD care, center designation will enhance the ability to undertake quality improvement and compare outcomes between SCD centers. Activities will include an assessment of the clinical effectiveness of expanded access to care, the implementation of SCD guidelines, and the efficacy of newly approved targeted medications. Details of this effort are provided.

Painful vaso-occlusive crisis (VOC) is the most common complication of sickle cell disease (SCD). Increasing evidence suggests that vaso-occlusion is initiated by increased adherence of sickle red blood cells (RBCs) to the vascular endothelium. Thus, the mechanisms that remove endothelial-attached sickle RBCs from the microvasculature are expected to be critical for optimal blood flow and prevention of VOC in SCD. We hypothesized that patrolling monocytes (PMos), which protect against vascular damage by scavenging cellular debris, could remove endothelial-adherent sickle RBCs and ameliorate VOC in SCD. We detected RBC (GPA+)-engulfed material in circulating PMos of patients with SCD, and their frequency was further increased during acute crisis. RBC uptake by PMos was specific to endothelial-attached sickle, but not control, RBCs and occurred mostly through ICAM-1, CD11a, and CD18. Heme oxygenase 1 induction, by counteracting the cytotoxic effects of engulfed RBC breakdown products, increased PMo viability. In addition, transfusions, by lowering sickle RBC uptake, improved PMo survival. Selective depletion of PMos in Townes sickle mice exacerbated vascular stasis and tissue damage, whereas treatment with muramyl dipeptide (NOD2 ligand), which increases PMo mass, reduced stasis and SCD associated organ damage. Altogether, these data demonstrate a novel mechanism for removal of endothelial attached sickle RBCs mediated by PMos that can protect against VOC pathogenesis, further supporting PMos as a promising therapeutic target in SCD VOC.

Painful vaso-occlusive crisis (VOC) is the most common complication of sickle cell disease (SCD). Increasing evidence suggests that vaso-occlusion is initiated by increased adherence of sickle red blood cells (RBCs) to the vascular endothelium. Thus, the mechanisms that remove endothelial-attached sickle RBCs from the microvasculature are expected to be critical for optimal blood flow and prevention of VOC in SCD. We hypothesized that patrolling monocytes (PMos), which protect against vascular damage by scavenging cellular debris, could remove endothelial-adherent sickle RBCs and ameliorate VOC in SCD. We detected RBC (GPA+)-engulfed material in circulating PMos of patients with SCD, and their frequency was further increased during acute crisis. RBC uptake by PMos was specific to endothelial-attached sickle, but not control, RBCs and occurred mostly through ICAM-1, CD11a, and CD18. Heme oxygenase 1 induction, by counteracting the cytotoxic effects of engulfed RBC breakdown products, increased PMo viability. In addition, transfusions, by lowering sickle RBC uptake, improved PMo survival. Selective depletion of PMos in Townes sickle mice exacerbated vascular stasis and tissue damage, whereas treatment with muramyl dipeptide (NOD2 ligand), which increases PMo mass, reduced stasis and SCD associated organ damage. Altogether, these data demonstrate a novel mechanism for removal of endothelial attached sickle RBCs mediated by PMos that can protect against VOC pathogenesis, further supporting PMos as a promising therapeutic target in SCD VOC.

Incremental improvement in care for children with sickle cell disease (SCD), arising from government-funded research over the last 4 decades, resulted in a dramatically reduced childhood mortality. However, the impact of iterative research and disease modifying therapy (DMT) on adults with SCD has not been as strong. Until now, there has been no coordinated, longitudinal, generalizable, natural history study of SCD that allowed for an assessment of the contemporary adult population.

Although the seminal event in sickle cell disease is the polymerization of abnormal hemoglobin, the downstream pathophysiology of vasoocclusion results from heterotypic interactions between the altered, adhesive sickle cell red blood cells, neutrophils, endothelium, and platelets. Ischemia reperfusion injury, hemolysis, and oxidant damage all contribute to heightened inflammation and activation of the hemostatic system. These various pathways are the focus of emerging treatments with potential to ameliorate disease manifestations. This review summarizes the considerable progress in development of these agents despite challenges in selection of study end points and complex pathophysiology.

Patients with sickle cell disease (SCD) suffer from intravascular hemolysis associated with vascular injury and dysfunction in mouse models, and painful vaso-occlusive crisis (VOC) involving increased attachment of sickle erythrocytes and activated leukocytes to damaged vascular endothelium. Patrolling monocytes, which normally scavenge damaged cells and debris from the vasculature, express higher levels of anti-inflammatory heme oxygenase 1 (HO-1), a heme degrading enzyme. Here, we show that HO-1–expressing patrolling monocytes protect SCD vasculature from ongoing hemolytic insult and vaso-occlusion. We found that a mean 37% of patrolling monocytes from SCD patients express very high levels of HO-1 (HO-1hi) vs 6% in healthy controls and demonstrated that HO-1hi expression was dependent on uptake of heme-exposed endothelium. SCD patients with a recent VOC episode had lower numbers of HO-1hi patrolling monocytes. Heme-mediated vaso-occlusion by mouse SCD red blood cells was exacerbated in mice lacking patrolling monocytes, and reversed following transfer of patrolling monocytes. Altogether, these data indicate that SCD patrolling monocytes remove hemolysis-damaged endothelial cells, resulting in HO-1 upregulation and dampening of VOC, and that perturbation in patrolling monocyte numbers resulting in lower numbers of HO-1hi patrolling monocyte may predispose SCD patients to VOC. These data suggest that HO-1hi patrolling monocytes are key players in VOC pathophysiology and have potential as therapeutic targets for VOC.

Patients with sickle cell disease (SCD) suffer from intravascular hemolysis associated with vascular injury and dysfunction in mouse models, and painful vaso-occlusive crisis (VOC) involving increased attachment of sickle erythrocytes and activated leukocytes to damaged vascular endothelium. Patrolling monocytes, which normally scavenge damaged cells and debris from the vasculature, express higher levels of anti-inflammatory heme oxygenase 1 (HO-1), a heme degrading enzyme. Here, we show that HO-1–expressing patrolling monocytes protect SCD vasculature from ongoing hemolytic insult and vaso-occlusion. We found that a mean 37% of patrolling monocytes from SCD patients express very high levels of HO-1 (HO-1hi) vs 6% in healthy controls and demonstrated that HO-1hiexpression was dependent on uptake of heme-exposed endothelium. SCD patients with a recent VOC episode had lower numbers of HO-1hipatrolling monocytes. Heme-mediated vaso-occlusion by mouse SCD red blood cells was exacerbated in mice lacking patrolling monocytes, and reversed following transfer of patrolling monocytes. Altogether, these data indicate that SCD patrolling monocytes remove hemolysis-damaged endothelial cells, resulting in HO-1 upregulation and dampening of VOC, and that perturbation in patrolling monocyte numbers resulting in lower numbers of HO-1hipatrolling monocyte may predispose SCD patients to VOC. These data suggest that HO-1hipatrolling monocytes are key players in VOC pathophysiology and have potential as therapeutic targets for VOC.

Sickle cell disease is an inherited hemoglobinopathy characterized by hemolytic anemia, frequent painful episodes, poor quality of life, end organ damage and a shortened lifespan. Although the seminal event is the polymerization of the abnormal hemoglobin, the downstream pathophysiology of vaso-occlusion results from heterotypic interactions between the altered, adhesive sickle cell RBCs, neutrophils, endothelium, and platelets. Ischemia reperfusion injury, hemolysis and oxidant damage all contribute to heightened inflammation and activation of the hemostatic system. These downstream targets are the focus of emerging treatments with considerable potential to ameliorate disease manifestations. This review summarizes the progress on development of these agents.

Introduction: Sickle cell disease (SCD) affects millions worldwide and is characterized by episodic severe pain, impacting quality of life and leading to significant healthcare utilization. Yet, clinicians face significant challenges in treating pain in individuals with SCD due to heterogeneity in pain experiences and pain impact. Improved understanding of the clinical characteristics of individuals with SCD who are at risk for developing severe pain is necessary to better manage pain and develop novel and personalized pain interventions. The objectives of this study were to (1) identify distinct pain subgroups based on demographic and psychosocial characteristics and (2) evaluate the relationship between the subgroups and pain impact.

The ability to characterize the modern person living with SCD in the US has been limited by the lack of a well-curated longitudinal registry. The Globin Research Network for Data and Discovery ( GRNDaD)registry aims to overcome this challenge by collecting data from the now 53 IRB-approved centers across the US in collaboration with the National Alliance of Sickle Cell Centers (NASCC) and the HRSA-funded Sickle Cell Disease Treatment Demonstration Project Grant. Here, we describe the use of disease-modifying therapy in (actively consented) adults and children with Hgb SS/ SB 0thalassemia (SCA) from 37 sites.

A multi-state, long term follow-up study of individuals with sickle cell disease (SCD) demonstrated an increase in mortality and morbidity in children and adults with COVID. mRNA vaccines are recommended for all SCD patients. Vaccination in individuals with SCD for other infections may be associated with impaired antibody responses. Concern has also been raised about whether mRNA vaccines, through a unique mechanism, may induce disease-related-complications in patients with SCD resulting in a suboptimal immunization rate. The ASH Research Collaborative Clinical Trial Network (ASH RC CTN) performed a mRNA vaccine trial to assess whether antibody responses following COVID vaccination were adequate to induce immunity and whether mRNA vaccination precipitated any toxicity unique to SCD patients. We prospectively studied patients at 8 of the ASH RC CTN sites: Johns Hopkins, Prisma, Duke, UT Southwestern, Medical College of Wisconsin, UCSF, Children's National, and Montefiore. Eligible patients with SCD had not yet received the COVID vaccine. We enrolled 59 patients and 47 received at least one vaccination. All vaccinated patients received the monovalent Pfizer vaccine. Forty-two patients received two vaccinations and provided baseline blood samples prior to vaccination and 2 months after the initial vaccination. For this report, data for 41 paired samples were available for analysis of IgG reactivity against the receptor binding domain (RBD) of the SARS-CoV-2 spike protein. Samples were taken from 7 patients (17%) under 3 years of age, 17 (41%) from older children (3-17 years of age), and 17 (41%) from adults (18-53 years of age). The majority of patients had HbSS (73%) or HbSC (22%), and one of each had either HbS beta 0 (2%) or HbS beta+ (2%). Concurrent therapies included hydroxyurea (59%), voxelotor (17%), crizulizumab (2%), intravenous immunoglobulin (2%), and chronic transfusions (2%). Five had a history of splenectomy (12%). Seventy-five percent of patients received their initial vaccination within 10 days of the baseline visit, and the median time between initial vaccination and post vaccination blood draw was 62 days. One patient experienced a COVID infection 5 days after the baseline visit, but prior to vaccination. This individual later received two vaccinations and submitted blood samples for analysis. Post-vaccination fever/chills, arthralgias, emesis, or local vaccination pain/erythema were reported in 49% of the patients. None reported fever that required inpatient admission. Seven patients (17%) reported a total of 8 episodes of vaso-occlusive pain within 14 days of the 1st vaccination. Of these, three required evaluation and treatment at a medical facility, and one patient was admitted for inpatient care. Antibody responses are shown in the Figure. Fourteen patients (34%) were seronegative at baseline, all with IgG ≤ 0.48 arbitrary units (AU). Twenty-seven patients (66%) were seropositive at baseline with a median IgG = 4.59 AU. Post-vaccination demonstrated a median IgG = 32.2 AU for the initially seronegative patients, and IgG = 102 AU for those initially seropositive. All initially seronegative patients converted to seropositive post vaccination; although post-vaccination IgG levels were lower than in the patients who were initially seropositive (Wilcoxon rank sum test, p-value = 0.0062). Overall, patients with sickle cell disease had side effects similar to those in the general population, and patients with SCD also responded to the COVID mRNA vaccination as expected after 2 months. The 6-month titers will be analyzed in the early fall. To our knowledge, this is the largest mRNA vaccine efficacy and safety trial in individuals with SCD, and it also marks the first evaluation of vaccine safety and antibody response in very young children with SCD.

Background:Acute painful vaso-occlusive crises (VOCs), the hallmark of sickle cell disease (SCD), are associated with chronic and potentially life-threatening complications. The SOLACE-adults study (NCT03264989) interim analysis (cutoff date: August 1, 2020) demonstrated the long-term pharmacokinetic (PK) and pharmacodynamic (PD) properties, potential sustained efficacy (VOC reduction), and long-term safety of crizanlizumab 5 mg/kg and 7.5 mg/kg during ≥12 months' (mo) treatment in >80% of patients (pts) with SCD [Kanter J et al . Blood advances2023]. Here we report the updated PK/PD, including ex vivo P-selectin inhibition, safety, and efficacy results from the final interim analysis of this study (cutoff date: June 1, 2022) for all pts who received crizanlizumab 5 mg/kg (~3.5 years [y]) and 7.5 mg/kg (~3 y).

Introduction: Acute chest syndrome (ACS) causes significant morbidity and mortality in both adult and pediatric sickle cell disease (SCD). Fifty to thirty percent of all pediatric SCD admissions develop ACS, with each episode potentially causing irreversible lung damage. Although there are some known risk factors for developing ACS (e.g., history of asthma), often this complication occurs unexpectedly. Our hypothesis was that a machine learning model could be developed to predict progression to ACS. Methods: A retrospective cohort study was designed to develop this prediction model. Data was abstracted from the electronic health record (EHR) from a single institution for all pediatric SCD admissions from 0-21 years old between June 1, 2016, and December 31, 2022. Inputs into the model included demographics (e.g., age, genotype), vital signs (e.g., heart rate, oxygen saturation), laboratory values (e.g., hemoglobin, neutrophil count), medication orders (e.g., albuterol, oxycodone) and additional co-morbidities (e.g., asthma, obstructive sleep apnea). The inputs had maximum and minimum values based on normal ranges by age. The output was a diagnosis of ACS as a continuous dependent variable to develop a continuous likelihood estimation score from 0 to 1. A positive output of ACS was defined as 2 doses of the antibiotic azithromycin and a chest x-ray ordered in the same encounter. The negative output included all patients who did not meet criteria for a positive output as defined above. Both positive and negative cohorts for ACS were included in the model. The time of ACS diagnosis was when the first dose of azithromycin was ordered. All ACS encounters were verified by chart review. A random forest model was implemented using Sklearn Python library. Different depth of trees was experimented between 1 to 24. A prediction for ACS was calculated every 6 hours after admission to the inpatient setting. Eighty percent of the data was used for training and twenty percent for testing. Results: Two thousand two hundred and sixty encounters were included in the negative cohort and 512 encounters were included in the positive cohort. One thousand four hundred and fourteen (51%) were male patients and 1358 were female patients (49%). The maximum depth of the tree was determined to be 10. Sixty-five percent of the positive cohort developed ACS 24 hours after the admission time. The median time that the random forest model predicted ACS was 18 hours before the diagnosis was determined in the chart. The model had a sensitivity of 80% and specificity of 64% at the cutoff point of 0.17. The area under the receiver operating characteristic (ROC) curve was 71%. The model's negative predictive value was 92% and the positive predictive value was 36% of diagnosing ACS. The features that were important predictors in the model were age, height, weight, pulse, respiratory rate, presence of hypoxia, temperature, neutrophil count, hemoglobin, absolute reticulocyte count and reticulocyte percent. Conclusion: A machine learning model demonstrated markers of hemolysis and vital sign changes were important to predict ACS in pediatric patients. This is the first model utilizing machine learning techniques in pediatric SCD to predict ACS. Detecting patients who are a higher risk for ACS could impact treatment options and approach to inpatient management.

Introduction: Despite disease-modifying effects of hydroxyurea (HU) on sickle cell disease (SCD), poor adherence among affected youth commonly impedes treatment impact. The HABIT multi-site randomized controlled efficacy trial aimed to increase HU adherence.

Introduction

Overcoming the silencing of the fetal γ-globin gene has been a long-standing goal in the treatment of sickle cell disease (SCD). The major transcriptional enhancer of the β-globin locus, called the locus control region (LCR), dynamically interacts with the developmental stage-appropriate β-type globin genes via chromatin looping, a process requiring the protein Ldb1. In adult erythroid cells, the LCR can be redirected from the adult β- to the fetal γ-globin promoter by tethering Ldb1 to the human γ-globin promoter with custom-designed zinc finger (ZF) proteins (ZF-Ldb1), leading to reactivation of γ-globin gene expression. To compare this approach to pharmacologic reactivation of fetal hemoglobin (HbF), hematopoietic cells from patients with SCD were treated with a lentivirus expressing the ZF-Ldb1 or with chemical HbF inducers. The HbF increase in cells treated with ZF-Ldb1 was more than double that observed with decitabine and pomalidomide; butyrate had an intermediate effect whereas tranylcypromine and hydroxyurea showed relatively low HbF reactivation. ZF-Ldb1 showed comparatively little toxicity, and reduced sickle hemoglobin (HbS) synthesis as well as sickling of SCD erythroid cells under hypoxic conditions. The efficacy and low cytotoxicity of lentiviral-mediated ZF-Ldb1 gene transfer compared with the drug regimens support its therapeutic potential for the treatment of SCD.

Overcoming the silencing of the fetal γ-globin gene has been a long-standing goal in the treatment of sickle cell disease (SCD). The major transcriptional enhancer of the β-globin locus, called the locus control region (LCR), dynamically interacts with the developmental stage-appropriate β-type globin genes via chromatin looping, a process requiring the protein Ldb1. In adult erythroid cells, the LCR can be redirected from the adult β- to the fetal γ-globin promoter by tethering Ldb1 to the human γ-globin promoter with custom-designed zinc finger (ZF) proteins (ZF-Ldb1), leading to reactivation of γ-globin gene expression. To compare this approach to pharmacologic reactivation of fetal hemoglobin (HbF), hematopoietic cells from patients with SCD were treated with a lentivirus expressing the ZF-Ldb1 or with chemical HbF inducers. The HbF increase in cells treated with ZF-Ldb1 was more than double that observed with decitabine and pomalidomide; butyrate had an intermediate effect whereas tranylcypromine and hydroxyurea showed relatively low HbF reactivation. ZF-Ldb1 showed comparatively little toxicity, and reduced sickle hemoglobin (HbS) synthesis as well as sickling of SCD erythroid cells under hypoxic conditions. The efficacy and low cytotoxicity of lentiviral-mediated ZF-Ldb1 gene transfer compared with the drug regimens support its therapeutic potential for the treatment of SCD.

Sickle cell disease (SCD) is a severe genetic blood disorder characterized by hemolytic anemia, episodic vaso-occlusion, and progressive organ damage. Current management of the disease remains symptomatic or preventative. Specific treatment targeting major complications such as vaso-occlusion is still lacking. Recent studies have identified various cellular and molecular factors that contribute to the pathophysiology of SCD. Here, we review the role of these elements and discuss the opportunities for therapeutic intervention.

Sickle cell disease (SCD) is a severe genetic blood disorder characterized by hemolytic anemia, episodic vaso-occlusion, and progressive organ damage. Current management of the disease remains symptomatic or preventative. Specific treatment targeting major complications such as vaso-occlusion is still lacking. Recent studies have identified various cellular and molecular factors that contribute to the pathophysiology of SCD. Here, we review the role of these elements and discuss the opportunities for therapeutic intervention.